Field of the Invention
The present invention relates to a gas storage/supply system and, more specifically, it relates to a gas storage/supply system of storing heat that is released upon absorption of a gas to a gas storage material in a chemical heat storage material and supplying heat that is necessary when the gas storage material desorbs a gas from the chemical heat storage material.
Description of the Related Art
“The gas storage material” means a material capable of reversibly absorbing and desorbing a gas such as hydrogen, ammonia, and methane. Generally, the gas storage material generates heat upon gas absorption and absorbs heat upon gas desorption.
The heat released during gas absorption (gas absorption heat) is usually discarded to the atmospheric air by way of a heat exchanger or the like and the heat necessary for gas desorption (gas desorption heat) is supplied from an external heat source. Accordingly, existent gas storage/supply systems involve a problem of low energy utilization efficiency.
For solving the problem, various proposals have been made so far.
For example, Patent Literature 1 discloses a hydrogen storing/supplying device including:
a hydrogen absorbing alloy,
a latent heat storage material (for example, CaCl2.6H2O) that stores heat from the hydrogen absorbing alloy upon absorption of a hydrogen gas and gives heat which is necessary when the hydrogen absorbing alloy desorbs the hydrogen gas,
a heat exchanger for conducting heat exchange with the hydrogen absorbing allay, and
a pressure container containing the hydrogen absorbing alloy, the latent heat storage material and the heat exchanger,
in which the latent heat storage material is housed in a plurality of sealed containers and mixed in the hydrogen absorbing alloy.
The reference describes that the device can decrease the energy for cooling and heating supplied from the outside without deteriorating the characteristics of absorbing and desorbing the hydrogen gas.
Patent Literature 2 discloses an absorption/desorption system of filling a hydridable material in a pressure resistant bottle, housing the pressure resistant bottle in a heat insulation container, and filling a heat storage medium (for example, molten sodium sulfate deca-hydrate) between the pressure resistant bottle and the heat insulation container.
The reference describes that the system provided with the heat storage medium can continuously release a greater amount of hydrogen over a longer time compared with a system not provided with the heat storage medium.
As described in the Patent Literatures 1 and 2, when gas absorption heat is stored by using the latent heat storage material, some of the gas desorption heat can be supplied from the latent heat storage material to the hydrogen absorbing alloy during gas desorption. Accordingly, more hydrogen can be desorbed compared with the case not using the latent heat storage material.
However, since the latent heat storage material has a low heat storage density, a large heat storage tank is necessary for ensuring a necessary quantity of heat. Further, since the time capable of storing heat is short, heat cannot be supplied at an optional timing.
Further, since the existent heat storage system has large sensible heat loss, all of the gas desorption heat released from the hydrogen absorbing alloy cannot be stored by the latent heat storage material and there is also a limit to the rate of heat exchange.